Dense spike-primrose (Epilobium densiflorum) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Dense Spike-primrose
Epilobium densiflorum

Species information

Epilobium densiflorum is a densely white-hairy annual herb arising from a taproot. Its leaves are essentially stalkless and alternate varying from elongate lance-shaped to ovate-lanceolate within the inflorescence. The rose-purple flowers are arranged in lateral spikes subtended by leafy bracts. The ripe capsules contain several seeds within each of the four chambers. Characteristically, the seeds lack the tuft of hairs (coma) that are present in most species of the genus.

Distribution

In Canada, Epilobium densiflorum occurs in southeast Vancouver Island. Its Canadian range extends north from Victoria to Nanaimo. It formerly occurred over a significantly larger area including Qualicum and North Pender Island. The nearest site outside Canada is on San Juan Island. The species ranges southward on both sides of the Cascades from Washington to Baja California and east to Idaho, Utah and Nevada. The species’ current range in Canada covers less than 1,000 km² and it actually occupies an area of less than 0.1 km².

Habitat

In Canada, Epilobium densiflorumoccurs within the Garry Oak Ecosystem in open meadows and ditches that are moist in spring and very dry in summer. An estimated 95% of the potential habitat has been lost over the past century due to agricultural, urban and industrial development along with fire suppression and invasion by exotic grasses and shrubs.

Biology

Epilobium densiflorum is an annual that flowers and fruits in mid- to late summer. It is predominantly self-pollinated but pollen may be transferred by bees and syrphid flies. The seeds are dispersed from the capsules in the late fall and winter. Unlike most species of Epilobium, the seeds lack a tuft of hairs (coma). As a result, they are not widely dispersed. The seeds germinate during the wet winter or spring but the plant continues to develop well into the summer drought period characteristic of southeast Vancouver Island. The ability to tolerate high moisture levels in the winter and very low moisture levels in the summer allows it to grow where many other plants would succumb to environmental stress.

Population sizes and trends

Old collection data are imprecise and different names may apply to the same location. It appears that Epilobium densiflorum has been collected from between 19 and 31 sites since it was first observed in British Columbia in 1887. Suitable habitats in its area of occurrence have been heavily studied in the past 20 years, revealing a sharp decline in the number of populations. Only four extant populations are known with population 2 being reduced to a single reproductive plant in 2003. The four Canadian populations have an aggregate of about 2,800-3,400 individuals. The populations are severely fragmented and there is negligible probability of recolonization of any population, once lost.

Limiting factors and threats

The primary threats to Epilobium densiflorum in Canada come from habitat destruction due to residential development, and habitat alteration due to changes in hydrology and invasive plants. The last large population is threatened by a proposed trailer park development. The key limitations are its requirement for a pronounced summer drought and wet, mild winters -- conditions that only prevail along a very restricted fringe of coastal habitat on and near southeast Vancouver Island.

Special significance of the species

The species, in Canada, likely represents a relict population that had a much broader distribution during the warm, dry Hypsithermal Interval, 4,000-6,000 years b.p. Aboriginal use of this species has been reported in a major ethnobotany database.

Existing protection or other status designations

Epilobium densiflorum has no species-specific protection in Canada or elsewhere. Only one of the four extant Canadian populations occurs in a protected area. The habitat where the one protected population occurs is threatened with encroachment by woody species.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal agencies (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government members and the co-chairs of the species specialist and the Aboriginal Traditional Knowledge subcommittees. The Committee meets to consider status reports on candidate species.

Definitions (November 2004)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)
A wildlife species that no longer exists.

Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A wildlife species facing imminent extirpation or extinction.

Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)Footnoteb
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)Footnotec
A wildlife species for which there is inadequate information to make a direct, or indirect, assessment of its risk of extinction.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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